(1) Field of the Invention
The present invention relates to a housing for fluid lubrication bearing apparatuses. Bearing apparatuses having this housing are suitable for information appliances, for example, in spindle motors for magnetic disk drive units such as HDD, optical disk drive units such as CD-ROM, CD-R/RW, DVD-ROM/RAM, magneto-optic disk drive units such as MD and MO, polygon scanner motors of laser beam printers (LBP), collar wheels of projectors, or electrical machinery and apparatuses, for example, small motors such as fan motors.
(2) Description of the Related Art
Enhanced speed, cost reduction, noise reduction, etc., as well as high rotational accuracy, are required for the above various kinds of motors. One of the components which determine these required performance is a bearing which supports spindles of said motors. In recent years, the use of a fluid lubrication bearing having excellent characteristics for the above required performance has been considered or actually used.
Fluid lubrication bearings of this type are roughly classified into: hydrodynamic bearings comprising a hydrodynamic pressure producing part for producing hydrodynamic pressure in a lubricating fluid within a bearing gap; and so-called cylindrical bearings (bearings having a bearing cross section in a perfect circle shape) without a hydrodynamic pressure producing part.
For example, in a fluid lubrication bearing apparatus integrated into a spindle motor of HDD and like disk drive units, a radial bearing portion which supports a shaft member constituting a rotational member in the radial direction and a thrust bearing portion which supports the shaft member in the thrust direction are both sometimes constituted by hydrodynamic bearings. An example of known radial bearing portions in fluid lubrication bearing apparatuses (hydrodynamic bearing apparatuses) of this type is such that hydrodynamic grooves are formed as a hydrodynamic pressure producing part on either the inner periphery face of a bearing sleeve or the outer circumferential surface of a shaft member opposing this and a radial bearing gap is formed between both faces. (For example, refer to Japanese Unexamined Patent Publication No. 2003-239951).
The above fluid lubrication bearing apparatus is constituted of a housing, bearing sleeve, shaft member and other parts. To ensure high rotational performance required for the increasingly high performance of information appliances, efforts to improve the dimensional accuracy and assembly precision of each part have been made. In contrast, with the trend of a decrease in the prices of information appliances, a demand for cost reduction in this type of bearing apparatuses is increasing. In response to these requirements, recently, forming a housing, a component part of a fluid lubrication bearing apparatus, of a resin material has been examined (for example, refer to Japanese Unexamined Patent Publication No. 2003-314534).
When fluid lubrication bearing apparatuses comprising these housings are integrated into and used in spindle motors for HDD and like magnetic disk apparatuses mentioned above, mounting of the fluid lubrication bearing apparatus onto a motor is normally carried out by adhesively fixing the outer circumferential surface of the housing on the inner periphery face of a motor bracket with an adhesive. However, when a resin forming the housing has poor adhesiveness, an adhesion surface is peeled by the impact caused by a drop of an information appliance integrating a magnetic disk apparatus, which may result in lowered function of the bearing apparatus and therefore of the magnetic disk apparatus. Particularly recently, in response to an increase in required disk capacities, the number of magnetic disks integrated into the above disk apparatus tends to increase. This further increases the impact force caused when dropped. Therefore, even higher adhesive force is required between a housing of this type and a motor bracket.
There are known means for improving the adhesiveness of a resin, for example, a method of adding a monoepoxy compound to a polyphenylene sulfide (PPS) resin (for example, refer to Japanese Unexamined Patent Publication No. H1-65171), or a method of adding a PPS resin modified with epoxy groups to an unmodified PPS resin (for example, refer to Japanese Unexamined Patent Publication No. H8-85759) and the like.